Transcript Minerals

Minerals
Take-Away Points
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Chemical elements form in stars
Atoms bond by sharing electrons
Minerals are classified by their chemistry
Minerals can be identified by their
physical properties = atomic structure
5. Silicates are the most important mineral
group
6. Crystals are determined by mathematical
rules called symmetry
Composition of the Sun
1. Chemical elements form in stars
Composition of the Sun
• Abundance of Light
Elements
• Rarity of Lithium,
Beryllium, Boron
• Preference for Even
Numbers
• Abundance peak at
Iron, trailing off after
1. Chemical elements form in stars
How Elements Form in Stars
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Sun: 4 H  He
He + particle  Mass 5 – Unstable
He + He  Mass 8 – Unstable
He + He + He  C
Add more He to make heavier elements
End of the line is iron for energy production
Atoms beyond Iron made in massive stars
1. Chemical elements form in stars
What are Planets Made of?
• Same material as Sun
• Minus the elements that remain mostly in
gases
• We find this pattern in a certain class of
meteorites
1. Chemical elements form in stars
Chondrites
1. Chemical elements form in stars
The Earth’s Crust looks Very
Different
1. Chemical elements form in stars
Composition of the Crust
1. Chemical elements form in stars
Minerals are the Chemicals that
make up the Earth
• Naturally Occurring
• Inorganic
• Chemical Compounds
• About 5000 Known
• 200 Common
• 20 Rock-Forming
Atomic Bonding
1. IONS
2. Atoms bond by sharing electrons
Atomic Bonding
2. Electrical Neutrality
• (+) and (-) Cancel Out
3. Bonding (Satisfy 1 & 2)
• Ionic (NaCl)
• Covalent (O2)
• Metallic (Cu, Al, Fe)
• Hydrogen (in water)
2. Atoms bond by sharing electrons
Ionic and Covalent Bonding
2. Atoms bond by sharing electrons
Metallic Bonding
2. Atoms bond by sharing electrons
Hydrogen Bonding
2. Atoms bond by sharing electrons
Summary of Bonding
• Ionic bonding holds rocks and minerals
together
• Covalent bonding holds people and other
organisms together
• Metallic bonding holds civilization together
• Hydrogen bonding gives water its heatretaining and solvent properties
2. Atoms bond by sharing electrons
4. Lattices
• Atoms in crystals form a repeating pattern
called a Lattice
2. Atoms bond by sharing electrons
5. Complex Anions (Radicals)
• Many minerals contain groups of atoms
that behave as single units
2. Atoms bond by sharing electrons
NAMING MINERALS
COLOR
• Glauconite (Greek: Glaucos = Blue-green)
OTHER PROPERTIES, USES
• Magnetite
COMPONENTS
• Chromite
PLACES
• Muscovite (Moscow)
PEOPLE
• Biotite
Chemicals (and Minerals) Are
Classified by their Anions
3. Minerals are classified by their chemistry
For Example: Iron Compounds
Have Little in Common
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Fe: Gray, Metallic
FeCl2: Light Green, Water Soluble
FeSO4: Light Green, Water Soluble
FeCO3: Brown, Fizzes in Acid
FeS2: Dense, Brittle, Metallic, Cubic Crystals
3. Minerals are classified by their chemistry
On the Other Hand, Sulfides have
Many Properties in Common
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FeS2
CuFeS2
PbS
ZnS2
All are Dense, Brittle, Metallic, have Cubic
Crystals
3. Minerals are classified by their chemistry
Identifying
Minerals
4. Minerals can be identified by their physical properties
Identifying Minerals
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Color: very variable, complex causes
Hardness: strength of atomic bonds
Density: mass and spacing of atoms
Luster: how electrons interact with light
Cleavage: weak atomic planes
Crystal Form: extremely useful but not for
beginners
• Other properties distinctive at times
4. Minerals can be identified by their physical properties = atomic structure
Color
• Sometimes Distinctive
• Often Unreliable
• Affected By:
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Chemical Impurities
Surface Coating
Grain Size
Weathering
4. Minerals can be identified by their physical properties = atomic structure
Hardness
• Resistance to Scratching
• Directly related to relative strength of
atomic bonds
• Scratch Test (Mohs)
• Indentation Test (Knoop)
Common Errors due to:
• Weathering, ‘Chalk' marks
• Breaking vs. Scratching
4. Minerals can be identified by their physical properties = atomic structure
Mohs vs. Knoop Scales
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Talc:
Gypsum, Fingernail:
Calcite, Penny:
Fluorite:
Apatite:
Feldspar, Glass:
Quartz:
Topaz:
Corundum:
Diamond:
very small
30
135
163
430
560
820
1340
2100
7000
4. Minerals can be identified by their physical properties = atomic structure
Density
• Directly related to masses of component
atoms and their spacing
• Usually very consistent
4. Minerals can be identified by their physical properties = atomic structure
Density - gm/cm3
(weight relative to water )
• Air:
0.001
Wood - Balsa: 0.1, Pine: 0.5, Oak: 0.6-0.9
Gasoline: 0.7, Motor Oil: 0.9
Ice:
0.92
Water:
1.00
Sugar:
1.59
Halite:
2.18
Quartz:
2.65
Most Major Minerals: 2.6-3.0
Aluminum: 2.7
4. Minerals can be identified by their physical properties = atomic structure
Density
• Pyrite, Hematite, Magnetite: 5.0
Galena:
7.5
Iron:
7.9
Copper:
9
Lead:
11.4
Mercury:
13.6
Uranium:
19
Gold:
19.3
Platinum:
21.4
Iridium: 22.4 (densest material on Earth)
4. Minerals can be identified by their physical properties = atomic structure
Luster
• Metallic or Nonmetallic is the most
important distinction.
• Resinous, waxy, silky, etc. are selfexplanatory.
• Vitreous is often used for glassy luster.
4. Minerals can be identified by their physical properties = atomic structure
Cleavage
• Tendency to split along smooth planes of
weaknessbetween atoms in crystal
• Directly related to atomic structure
• Related to Crystal Form
• Every cleavage face is a possible crystal face
• Not every crystal face is a cleavage face.
Quartz commonly forms crystals but lacks
cleavage.
4. Minerals can be identified by their physical properties = atomic structure
Other Properties
Crystal Form
• Takes Luck & Practice
• Well-formed crystals are uncommon
• Crystal Classification is somewhat subtle
Fracture
4. Minerals can be identified by their physical properties = atomic structure
Identifying Minerals
Geologic Setting
• Some minerals occur in all geologic
settings: quartz, feldspar, pyrite
• Some minerals occur mostly in sedimentary
settings: calcite, dolomite
• Some minerals occur mostly in igneous
settings: olivine
• Some minerals occur mostly in
metamorphic settings: garnet, kyanite
4. Minerals can be identified by their physical properties = atomic structure
Identifying Minerals
Special Properties
• Taste, Magnetism, Etc.
Experience and Reading
• “The best geologist is the one who’s seen
the most rocks.”
Professional Methods
• Chemical Analysis
• X-Ray Studies
• Thin Section
4. Minerals can be identified by their physical properties = atomic structure
Diffraction
4. Minerals can be identified by their physical properties = atomic structure
Diffraction
4. Minerals can be identified by their physical properties = atomic structure
A Common Example
Diffraction in Opal
4. Minerals can be identified by their physical properties = atomic structure
MAJOR MINERAL SUITES
Elements
Metallic:Au, Ag, Cu
• Not Al, Pb, Zn, Fe, etc.
Nonmetallic: C - Diamond, Graphite
• Sulfur
4. Minerals can be identified by their physical properties = atomic structure
Copper Nugget
MAJOR MINERAL SUITES
Sulfides: Dense, Usually Metallic
Many Major Ores
• Pyrite FeS2
• Chalcopyrite CuFeS2
• Galena PbS
• Sphalerite ZnS2
• Molybdenite MoS2
4. Minerals can be identified by their physical properties = atomic structure
MAJOR MINERAL SUITES
Halides: Usually Soft, Often Soluble
• Halite NaCl
• Fluorite CaF2
Sulfates: Soft, Light Color
• Gypsum CaSO4
• Barite BaSO4
4. Minerals can be identified by their physical properties = atomic structure
MAJOR MINERAL SUITES
Oxides: Often Variable, Some Ores
• Hematite Fe2O3
• Bauxite Al(OH) 3 (a hydroxide)
• Corundum Al2O3 (Ruby, Sapphire)
Carbonates: Fizz in Acid, Give off CO2
• Calcite CaCO3
• Dolomite CaMg (CO3)2
4. Minerals can be identified by their physical properties = atomic structure
MOST IMPORTANT MINERAL
SUITE:
The Silicate Minerals
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Si + O = 75% of Crust
Silicates make up 95% + of all Rocks
SiO4: -4 charge
Link Corner-To-Corner by Sharing Oxygen
atoms
Nesosilicates - Isolated
Tetrahedra
Representatives:
•Garnet
•Kyanite
•Olivine
5. Silicates are the most important mineral group
Sorosilicates - Paired Tetrahedra
Epidote is the
most common
example
5. Silicates are the most important mineral group
Cyclosilicates - Rings
•Beryl (Emerald)
•Tourmaline
5. Silicates are the most important mineral group
Inosilicates - Chains
Single Chains (Pyroxenes)
5. Silicates are the most important mineral group
Inosilicates - Chains
Double Chains (Amphiboles)
5. Silicates are the most important mineral group
Phyllosilicates - Sheets
5. Silicates are the most important mineral group
Phyllosilicates - Sheets
Si2O5 sheets with layers of Mg(OH)2 or Al(OH)3
• Micas
• Clay minerals
• Talc
• Serpentine (asbestos) minerals
5. Silicates are the most important mineral group
One Type of Asbestos
5. Silicates are the most important mineral group
Tectosilicates - ThreeDimensional Networks
• Quartz
Feldspars
5. Silicates are the most important mineral group
Making Sense of Crystals
6. Crystals are determined by mathematical rules called symmetry
Unit Cells
All repeating patterns can be described in
terms of repeating boxes
The problem in Crystallography is to reason
from the outward shape to the unit cell
6. Crystals are determined by mathematical rules called symmetry
Which Shape Makes Each Stack?
Crystals are determined by mathematical rules called symmetry
Stacking Cubes
6. Crystals are determined by mathematical rules called symmetry
6. Crystals are determined by mathematical rules called symmetry
6. Crystals are determined by mathematical rules called symmetry
6. Crystals are determined by mathematical rules called symmetry
Some shapes that result from
stacking cubes
6. Crystals are determined by mathematical rules called symmetry
Symmetry – the rules behind the shapes
6. Crystals are determined by mathematical rules called symmetry
Symmetry – the rules behind the shapes
6. Crystals are determined by mathematical rules called symmetry
The Crystal Classes
6. Crystals are determined by mathematical rules called symmetry
Take-Away Points
1.
2.
3.
4.
Chemical elements form in stars
Atoms bond by sharing electrons
Minerals are classified by their chemistry
Minerals can be identified by their
physical properties = atomic structure
5. Silicates are the most important mineral
group
6. Crystals are determined by mathematical
rules called symmetry